基于微纳结构调控的高热导率石墨烯薄膜制备与热传输机理研究

With the development towards miniaturization, high performance and multi-functionality, thermal dissipation issues are critical due to tremendous heat fluxes generated. Currently, the pyrolytic graphite sheets (PGS) based on carbonization, natural graphite film and graphene film can not meet the need of thermal dissipation, so the market is in desperate need of a graphene film with higher thermal conductivity. The purpose of this project is to investigate phonon transport mechanisms in graphene layered structures and to develop highly oriented microscale thick graphene films (GFs) that have in-plane thermal conductivity above 3500W/mK, hopefully in the range up to 5000-10000W/mK or even higher and with robust mechanical strength in a thickness ranging from a few hundreds of nano- to micrometers. Firstly, the influence of lateral size, concentration, oxygen contents and self-assembly of graphene oxide (GO) on film quality will be investigated. Secondly, the effect of micro-nano structure of graphene film on thermal conductivity will be carried out by optimizing the parameters of graphitization and pressing conditions to improve the turbostractic portion of the graphite structure and density. Thirdly，mechanical property of graphene film will be analyzed. Finally, simulation and modeling via molecular dynamic simulation method will be carried out to understand the effect of micro-nano structure of graphene film on phonon transfer.

随着电子产品日趋小型化、多功能化和高性能化，单位面积上产生的热量也急剧上升，所以散热成为至关重要的问题。目前市场上的碳化石墨膜、天然石墨膜以及石墨烯薄膜的热导率还不能够满足需求，需开发高热导率的石墨烯薄膜。本项目将主要研究石墨烯层状结构内声子传输机理并开发高取向性高热导率的微米级厚度的石墨烯薄膜，使得石墨烯薄膜面内热导率高于3500W/mK，甚至达到5000-10000W/mK，同时使得薄膜在几百纳米至微米厚度范围内具有较高的机械强度。首先，研究石墨烯薄膜前驱体氧化石墨烯的尺寸、含氧量、浓度以及氧化石墨烯溶液的自组装技术对成膜质量的影响；其次，研究石墨烯薄膜微纳结构对石墨烯薄膜热导率的影响，通过优化石墨化和压延的工艺参数提高石墨烯薄膜的无序结晶度、密度；然后，对石墨烯薄膜进行机械性能分析；最后，通过分子动力学模拟计算，阐释石墨烯薄膜微纳结构对声子传输的影响。

电子产品的小型化和高集成度对散热材料提出了更高要求，目前市场上的碳化石墨膜、天然石墨膜以及石墨烯薄膜的热导率还不能够满足需求，需开发高热导率的石墨烯薄膜。本项目对石墨烯薄膜前驱体氧化石墨烯的材料属性、氧化石墨烯取向工艺、石墨化工艺、压延工艺等与热导率之间的关系展开了深入系统的研究，从而完成石墨烯的可控组装。项目在以下几个方面取得了创新成果：1）超高热导率石墨烯薄膜的制备技术。通过优化自组装工艺、石墨化工艺和压延工艺，制备得到超高热导率3826±47W/(m·K)的石墨烯薄膜（1μm）。2）高热导率石墨烯厚膜的制备技术。通过对单层亚微米氧化石墨烯连续高压均质加工工艺的优化，制备得到热导率为1204±35 W/(m·K)的石墨烯厚膜（75μm）。项目的开展，为高导热石墨烯膜在高功率密度电子产品中大规模应用提供了科学基础。